1. Field of the Invention
This invention relates to apparatuses and methods for applying sleeves to objects, and more particularly, for placing plastic sleeves on objects in a continuous cycle at very high speeds.
2. Reference to Patents and Applications
"Control Marking Detector," U.S. Pat. No. 4,392,056.
"Labeling Apparatus," U.S. Pat. No. 4,412,876.
"Non-Migrating Control Indicia for a Plastic Web or Sheet Article," U.S. Pat. No. 4,467,207.
"Automated Manufacturing Monitoring," U.S. Pat. No. 4,565,592.
"Labeling Apparatus," U.S. Pat. No. 4,620,888.
"Continuous Web Registration," U.S. Pat. No. 4,680,205.
"Process for Performing Work on a Continuous Web," U.S. Pat. No. 4,926,048.
"Continuous Web Registration," U.S. Pat. No. 4,945,252.
"Labeling Apparatus," U.S. Pat. No. 4,944,825.
"Method and Apparatus for Registering Bottles," application Ser. No. 07/708,509.
3. Background Information
The labeling of product containers such as bottles, can be done by various methods. Early methods involved either printing information directly onto the container or alternatively printing the information on a label which was then adhesively bonded to the container. Machines which wrap an adhesive label around a bottle have been developed which have production rates in excess of 300 bottles per minute.
Recently, it has become popular to label bottles with tubular, flexible, plastic sleeves without adhesives. In particular, non-adhesive sleeves have become popular for labeling plastic "two liter" bottles commonly used for soft drinks.
When an adhesive label is used on a plastic bottle, the portion of the bottle contacting the adhesive is not economically recoverable with conventional recycling processes. When non-adhesive sleeves are used, the sleeve and all or most of the bottle is recoverable because the sleeve is easily separated from the bottle. Some governments have passed, and it is expected that others will pass, laws mandating fully recoverable bottles.
Apparatuses and methods for automatically placing tubular non-adhesive sleeves on empty containers have been developed. More recently, apparatuses and methods for applying sleeves to filled bottles have been developed by the present assignee with considerable success. These are disclosed in the assignee's referenced patents for "Labeling Apparatus" and in the assignee's co-pending application for "Method and Apparatus for Registering Bottles."
Labeling filled bottles presents special problems for labeling machines due to the added mass of the fluid contents and the effect of the fluid contents moving within the bottle. Further provision must be made for the possibility that a labeling machine malfunction may cause a filled bottle to be crushed resulting in the contents being released.
In the labeling industry, there is a great demand for non-adhesive labeling machines which have high production rates and which can label either filled or empty bottles. Heretofore, the present assignee has been able to achieve sleeving rates of approximately 90 bottles per minute with the apparatuses of the referenced patents. This rate is sufficient for many applications, however, it is less than what can be achieved with adhesive, wrap-around label machines.
With sleeving apparatuses of the referenced patents and in most prior art machines and processes, the bottles are stopped before the sleeve is applied and accelerated afterwards. Starting and stopping the bottles greatly limits the production rate of a machine. Therefore, there has been a great need for a machine which can apply non-adhesive sleeves to bottles, whether full or empty, while the bottles are moving at high speeds. In addition, there is a demand for machines which take up less space, are able to accommodate varying bottle shapes and sizes, are able to position sleeves on objects with a high degree of accuracy, and have a low frequency of product damage.
In prior art sleeving machines such as the assignee's Labeling Apparatus disclosed in U.S. Pat. No. 4,620,888, the thickness of the sleeves is very critical. The thickness of the sleeve is generally a function of the frictional forces between the sleeve and the bottle. These frictional forces vary widely depending on the characteristics of the sleeve and the bottle.
The effort to pull the sleeve over the bottles is resisted by the frictional forces between the sleeve and bottle. Sleeves for bottles are initially smaller in diameter than the bottle being sleeved. Thus, each sleeve is stretched as it is pulled over each bottle. Other factors can exacerbate the frictional resistance to pulling a sleeve over a bottle. For example, some types of plastic used for bottles such as polyethylene have a low friction surface, but others such as PET material have a very high friction surface. Some labels have printing on their inside surfaces. Such printing increases the friction between the sleeve and the bottle. Thicker sleeves are more difficult to pull down over a bottle because they resist stretching and thus increase sleeve-bottle friction. Some bottles have shoulders over which a sleeve must be stretched. Additives may be added to the sleeve material to make them more stretchable, however, this adds to the cost of the sleeves.
In general, it is desirable to use thinner sleeves. Thinner sleeves contain less material and are thus less costly. However, in some applications, it is desirable to use a thicker sleeve. For example, some bottles rely on a heavy sleeve for added hoop strength. Thus, in prior art machines, for a given bottle type and sleeve requirement, the sleeve thickness and sleeve material ingredients are painstakingly selected. There is a need for a sleeving machine which permits greater flexibility in matching sleeve thicknesses and sleeve types to particular applications.